Ceramic bodies having internal honeycomb structures defined by porous walls have several uses, e.g., as solid particulate filter bodies and as stationary heat exchangers. Such uses require selected channels of the structure to be sealed or plugged by manifolding and the like at one or both of the respective ends thereof.
In the operation of a ceramic plugged filter, a contaminated fluid or gas is brought under pressure to an inlet face and enters the ceramic filter body via those channels with open ends at the inlet face. Because these channels are sealed at the opposite (outlet) face, the contaminated fluid is forced through the thin porous walls into adjoining channels. The solid particulate contaminant in the fluid, which is too large to pass through the porous openings in the walls, is left behind, and a cleansed fluid exits the filter through the outlet channels.
Sealing the channels involves inserting a plugging material into the open ends of select channel channels, and subsequently drying the plugged filter. Previous methods for forming a plugged honeycombed structure include forming an extruded ceramic-based green honeycomb structure, drying the structure in an oven, plugging the open ends of select channels, and firing the resultant plugged honeycomb structure.
The plugging methods can potentially lead to defects in the plugs, which cause filter leaks. The channels of the honeycomb structure can also be obstructed within the ceramic filter body itself due to the collapse of a channel wall, or if excess material remains in the channels. It is therefore important in the filter manufacturing process to be able to quickly and efficiently inspect the ceramic filter bodies for defects that could ultimately cause leaks in the subsequently formed filter.